A wireless communications system is engineered to serve a desired level of traffic according to radio transmission characteristics that are assumed to provide homogeneous signal strength coverage over a defined geographic area and are assumed to be time invariant. However, radio conditions between mobile subscriber units and serving base stations change with time, which degrades the performance of the wireless communications system (possibly substantially). Degradation of the wireless communications system's performance can be manifested in a number of ways. Examples include an increased dropped call rate and an increased frame error rate. The wireless communications system may require periodic “retuning” of base station antennas in order to maintain the engineered performance objectives. Each retuning of a base station may require that a technician physically travel to a base station's location. The effort associated with retuning is amplified by the number of base stations (which may be in the hundreds) associated with the wireless communications system. Thus, the task of retuning the wireless communications system is labor-intensive, time-consuming and expensive.
Additionally, radio characteristics are usually not homogeneous within a serving area of a base station antenna. Within the serving area, factors such as buildings, foliage, terrain and weather are not homogeneous, causing radio characteristics not to be homogeneous. Moreover, these factors may change with time, e.g. new buildings are constructed within the service area and the leaves of trees grow and fall with the seasons of the year. These phenomena cause “holes” in the radio coverage area. Increasing the signal strength in the direction of the hole can compensate for the deficiency.
With the prior art, “drive tests” are periodically conducted in order to detect holes in radio frequency (RF) coverage. Drive tests require that technicians operate mobile subscriber units while traversing routes and collecting measurements within the coverage area of the wireless communications system. The measurements are typically stored on a recording medium attached to the mobile subscriber unit. The measurements are subsequently analyzed to evaluate the RF coverage as provided by the wireless communications system.
A base station serves a region called a cell, which is further partitioned into sectors. The base station serves multiple sectors of a cell with each sector corresponding to a base station antenna. Because RF characteristics may not be homogeneous within a sub-region (sub-sector) of a sector, each base station antenna (sector) may require adjustments that are dependent upon a subregion of the given sector. Periodic retuning (that is typical with the prior art) must therefore account for the heterogeneous nature of RF characteristics. Thus, the wireless industry has a definite and urgent need for an invention that allows a wireless service provider to automatically retune the base station antennas within the wireless communications system in order to provide better service at a lower cost.